Inhibition of corrosion

ABSTRACT

The corrosion of metal surfaces which are subject to corrosion when contacted with an organic substrate such as a jet fuel and water is inhibited by incorporating in the organic substrate a corrosion inhibiting concentration of a secondary amine comprising a carboxylic acid salt of an N,N-disubstituted amine.

United States Patent 1191 1111 Goeller July 8, 1975 {54] INHIBITION OF CORROSION 2,736,658 1/1956 Pfohl 44/66 X 2,758,086 8 1956 St rt t 44 66 X [75] inventor: Leonhard A. Goeller, Des Plames, 2851345 911958 gi i alm M 24/66 3,084,034 4/1963 Kalinowski..... 44/66 Assigneez i sa Products pa y, Reese et al. Des Plaines, Ill. Primary Examiner-Daniel E. Wyman [22] 1973 Assistant Examiner--Y. H. Smith ['21 Appl. No.: 321,888 Attorney, Agent, or Firm.lames R. l-loatson, IL;

Related U 5 Application Data Raymond H. Nelson; William H. Page, II [63] Continuation-impart of Ser. No. 103,001, Dec. 30,

R970. abandoned. [57] ABSTRACT The corrosion of metal surfaces which are subject to [52] US. Cl. 44/66, 44l7l252/l3gg corrosion when contacted with an organic substrate [51 illll. Cl /92 such as a jet fuel and water is inhibited y incorporat L5 8] Flew of Search /3 ing in the organic substrate a corrosion inhibiting concentration of a secondary amine comprising a carbox- References cued ylic acid salt of an N,N-disubstituted amine.

UNITED STATES PATENTS 2,330,524 9 1943 Shields 44 71 2 Clam, D'awmgs INHIBITION OF CORROSION CROSSREFERENCE TO RELATED APPLICATIONS This application is a continuationinpart of my co pending application Ser. No. 103,001 filed Dec. 30, I970 now abandoned.

BACKGROUND OF THE INVENTION In the manufacture. handling. transportation and/or use of various organic substances, corrosion problems occur due to the presence of varying amounts of water in solution or in suspension in the organic substances. Illustrative organic substances include particularly hydrocarbon distillates as gasoline, jet fuel, kerosene, lubricating oil, fuel oil, diesel oil, crude oil, etc. Other illustrative oils include cutting oil, soluble oil, slushing i)ll, rolling oil, etc. which may be of mineral, animal or vegetable origin. Other organic substances include various coating compositions as grease, wax, household oil. paints. lacquer, etc. Still other organic substances include alcohols, ketones. esters, ether, dioxane, amldCS, etc. In spite of all reasonable and practical precautions which are taken to avoid the presence of water, an appreciable quantity of water separation is found as a film or as minute droplets in the pipeline or on container walls or even in small pools at the bottom of the container. This results in corrosion of the metal surfaces and contamination of the organic substance by the corrosion products.

The avoidance of corrosion of the metal surfaces is to be avoided in many instances. This is especially true in fuel tanks of aircraft, both military and commercial in nature, which contain the jet fuels necessary to power the engines in modern airplanes. In order to prevent this corrosion, it is necessary to incorporate in the et fuel a substance which possesses the ability to pass the most severe water tolerance tests. Among the corrosion inhibitors which have been proposed in the prior art are carboxylic acid salts of primary amines or polyamines which Contain, in addition to secondary amines, a primary amine group. While such salts may be effective in varying degree to inhibit corrosion of metal surfaces, the use of such salts will result in emulsification problems due to the poor water tolerance of the inhibitors. Because of this, such corrosion inhibitors do not meet military specifications as to water tolerance. This is true in the case of a water tolerance test known as the Water Separometer Index Modified Test commonly referred to as WSIM. This test will be hereinafter described in specific detail in the following specification, The inability to pass a severe water tolerance test such as the WSIM test for compounds such as alkyl propy- .Iene-diamine salts which have been disclosed in the prior art graphically illustrates the difference between these compounds and the carboxylic acid salts of secondary amines of the present invention. In addition, in contrast to the other compounds set forth in the prior art. it has been unexpectedly discovered that the secondary amine salts of the present invention are not equivalent to primary or tertiary amine salts.

DESCRIPTION OF THE INVENTION The present invention relates to novel corrosion inhibitors which also possess the ability to pass water tolerance tests. Accordingly, these corrosion inhibitors will pass military specifications which have been laid down for the use of inhibitors in substrates such as jet fuels.

It is therefore an object of this invention to provide corrosion inhibitors which will pass water tolerance tests.

In one aspect an embodiment of this invention relates to jet fuel which is corrosive to metal on contact with water containing, as an inhibitor against corrosion, a corrosion inhibiting concentration of a secondary amine comprising a carboxylic acid salt of an N,N- dialiphatic-amine or a carboxylic acid salt of an N,N-dicycloaliphatic-amine.

The N,N-dialiphatic-amine preferably contains from I to 50 carbon atoms and more preferably from 4 and still more particularly from 8 to 30 carbon atoms in each aliphatic group. Preferably the aliphatic substituents are the same and, in a particularly preferred embodiment, the aliphatic groups are alkyl substituents which may be straight or branched chain. Thus, the preferred alkyl substituents are selected from octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl and triacontyl. In another embodiment the alkyl substituents are selected from methyl, ethyl, propyl, pentyl, hexyl and heptyl. In still another embodiment the alkyl substituents are of different chain length and/or configuration.

In a preferred embodiment, the alkyl substituents are derived from fatty acids. A number of these dialkylamines are available commercially at comparatively low cost, such as hydrogenated N,N-ditallowamine, N,N- disoyaamine, N,Ndicocoamine, etc. These fatty acids derived diamines are hydrogenated and thus are substantially free from unsaturation in the aliphatic substituents. These commercially available low cost secondary amines comprise a mixture of amines. For example, N,N-ditallowamine contains a mixture of amines having 14 to 18 and predominately 16 to 18 carbon atoms in each aliphatic substituent. The commercially available N,N-dicocoamine contains aliphatic substituents of 8 to 18 carbon atoms each and predominates in aliphatic substituents of 12 and 14 carbon atoms each. N,N-disoyaamine contains predominately 16 to 18 carbon atoms in each aliphatic substituent. Another commercially available secondary amine is Kemamine S-l which predominates in aliphatic substituents containing 20 to 22 carbon atoms each.

While the N,N-dialkylamines are preferred, it is understood that the corresponding N,N-dialkenylamines may be used but not necessarily with equivalent results. Preferred alkenyl substituents contain from 8 to 30 carbon atoms each and thus will be selected from octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, octadecenyl, nonadecenyl, eicosenyl, heneicosenyl, docosenyl, tricosenyl, tetracosenyl, pentacosenyl, hexacosenyl, heptacosenyl, octacosenyl, nonacosenyl and triacontenyl. Here again mixture derived from fatty acids are available commercially at comparatively low cost and accordingly are preferred for use in forming the salt.

In still another embodiment the secondary amine for use in forming the salt is N,N-dicycloaliphatic-amine, preferably containing from 4 to 12 and more preferably from 5 to 8 carbon atoms in the ring. Illustrative N,N-

dicycloalkylamines include N,N-dicyclopentylamine, N,N-dicyclohexylamine, N,N-dicycloheptylamine. N.N-dicyclooctylamine. N,N-dicyclononylamine. N,N-dicyclodecylamine. N.N- dicycloundecylamine and N.N-dicyclododecylamine. Corresponding amines containing unsaturation in the ring may be used but not necessarily with equivalent results.

From the above discussion. it will be seen that any suitable secondary amine may be used in accordance with the present invention. In one embodiment this may include N,N-diall ylamines in which the alkyl groups are the same or different. In another embodiment the secondary amine may contain both saturated and unsaturated aliphatic substituents. In still another embodiment the substituents may comprise both aliphatic and cycloaliphatic substituents. It is understood that these differently substituted secondary amines are not necessarily equivalent for use in preparing salts for use as corrosion inhibitors.

Any suitable carboxylic acid is used in preparing the salt for use in the present invention. The carboxylic acid may contain from I to 50 carbon atoms and preferably contains from 4 to 40 carbon atoms. In one embodiment the carboxylic acid is selected from acids as formic, acetic, propionic, trimethylacetic, pelargonic. etc. In a preferred embodiment the carboxylic acid is a saturated fatty acid and is selected from butyric, valeric, caproic, caprylic, lauric, capric. myristic, palmitic, stearic, arachidic, behenic, lignoceric, cerotic, etc. In another embodiment the carboxylic acid is an unsaturated carboxylic acid and will be selected from acrylic, methacrylic, crotonic, butenoic, pentenoic, hexenoic, heptenoic, octenoic, and nonenoic. Here again the carboxylic acid preferably is a fatty acid and will be selected from decylenic, stillingic. dodecylenic, palmitoleic, oleic, petroselenic, vaccenic. linoleic. linolenic, eleostearic, Iicanic, parinaric, gadoleic. arachidonic, cetoleic, erucic, selacholeic, etc

In still another embodiment the carboxylic acid is a hydroxycarboxylic acid. Illustrative examples in this embodiment include hydroxyacetic acid, hydroxypropionic acid and conveniently hydroxyfatty acids including hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxycaprylic acid, hydroxycapric acid, hydroxylauric acid, hydroxymyristic acid, hydroxypalmitic acid, hydroxystearic acid, hydroxyarachidic acid, hydroxybehenic acid, hydroxylignoceric acid, hydroxycerotic acid, hydroxydecylenic acid, hydroxystillingic acid, hydroxydodecylenic acid, hydroxypalmitoleic acid, hydroxyoleic acid, hydroxypetroselinic acid, hydroxyvaccenic acid. hydroxylinoleic acid, hydroxylinolenic acid, hydroxyeleostearic acid, hydroxypar-inaric acid, hydroxygadoleic acid, hydroxyarachidonic acid, hydroxycetoleic acid, hydroxyerucic acid, hydroxyselacholeic acid, etc. In one embodiment the hydroxy group is attached to a terminal carbon atom and. in another embodiment. it is attached in the chain as, for example. in ricinoleic acid, lactic acid, etc,

In still another embodiment a polycarboxylic acid and preferably a dicarboxylic acid may be used in forming the salt. Illustrative examples in this embodiment include acids as oxalic, malonic. succinic, glutaric. maleic, fumaric, glutaconic, adipic. pimelic. suberic, aze laic, sebacic, dodecanedioic. octenedioic, etc., and particularly the alkyl or alkenyl substituted acids.

N.N-dicyclobut vlamine,

In still another embodiment the carboxylic acid is a comparatively low cost dimeric acid available commercially under names as VR-l." D-50 MEX," DI- MER." EMPOL I014" and similar acids. In general, the dimeric acid is a dilinoleic acid and contains predominately 36 carbon atoms per molecule. Still another low cost carboxylic acid is available under the tradename Resin 73I-D which predominates in abietic acid derivatives.

It is understood that the carboxylic acid salts ofa secondary amine formed from these different acids are not necessarily equivalent in their effectiveness as corrosion inhibitors. Also, it is understood that a mixture of the carboxylic acids may be used in preparing these salts.

The carboxylic acid salt ofa secondary amine for use in the present invention is prepared in any suitable manner and generally by intimately mixing the amine and acid under conditions to avoid substantial conversion to amide, ester or other condensation reactions. In one embodiment substantially equal molar proportions of the secondary amine and acid are used. However, when desired, an excess of the secondary amine or acid may be employed and thus the proportions will be in the range of from 0.5 to 2 basic equivalents of amine per 0.5 to 2 acidic equivalents of acid. It is understood that the acidic equivalents will depend upon whether a mono or polycarboxylic acid is used. In one method, the reactants are admixed and stirred in the absence of a solvent, in which case it is preferred to warm one or both of the reactants prior to mixing, especially when solid at room temperature. For example, the secondary amine may be a solid and preferably is heated to a temperature of from about 29 to 77 C. for ease of handling and reacting. In another method, the salt is formed in the presence of a suitable solvent. Suitable solvents include aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, cumene or mixtures thereof, paraffinic hydrocarbons such as hexane, heptane, octane, nonane, decane, undecane, dodecane, etc., or a mixture thereof, or a mixture of aromatic, paraffinic and/or naphthinic hydrocarbons as, for example, in naphtha, kerosene, light fuel oil. diesel oil, or other suitable mixtures.

The secondary amine and acid are intimately stirred at a temperature of from about 29 to 77 C., although a higher temperature, up to about C., may be used. For economical reasons the temperature of heating will be as low as required for the convenient handling and mixing of the reactants. The time of mixing will be sufficient to insure substantially complete reaction and may range from 15 minutes to 8 hours or more.

In most cases the final product will comprise substantially l00% by weight of the carboxylic acid salt of a secondary amine. However, when an excess of one reactant is employed. the product will contain unreacted amine or acid. When the salt is prepared under a relatively high temperature, the product may contain a minor amount of amide, ester or both.

The carboxylic acid salt ofa secondary amine may be utilized as such. although generally it is preferred to prepare the salt as a solution in a suitable solvent for ease of handling and measuring. Any suitable solvent may be employed and advantageously is selected from the solvents hereinbefore set forth.

The carboxylic acid salt of a secondary amine is used in a sufficient concentration to effect the desired corrosion inhibition. For economical reasons, the salt is used in a low concentration and thus may be within the range of from about to about 50 ppm (parts per million). However, in some applications. higher concentrations may be used. which may range up to 0.1% or more by weight of the substrate.

The carboxylic acid salt of a secondary amine is incorporated in the substrate such as ajet fuel in any suitable manner. When the aforementioned salt is prepared as a solution it may be utilized as such. When the carboxylic acid salt of a secondary amine is prepared in the absence ofa solvent, it may be formed as a solution in any suitable solvent, preferably being selected from those hereinbefore set forth. for ease in handling, measuring and use. The salt is added to the substrate in any suitable manner, preferably with mixing in order to insure even distribution of the salt in thejet fuel substrate.

As hereinbefore set forth the aforementioned carboxylic acid salt of a secondary amine is especially useful as a corrosion inhibitor in an organic substrate such as get fuel which causes corrosion of the metal surfaces when said substrate contains an amount of water. The aforementioned salt is particularly useful in hydrocarbon substrates in which water emulsification specifications are important. While the present invention is primarily concerned with liquid hydrocarbon substrates which cause corrosion problems, it is also contemplated within the scope of this invention that the carlboxylic acid salt ofa secondary amine may also be soluble in hydrocarbon gas such as propane, butane, or mixtures thereof and therefore the salt of the present invention may be used to inhibit corrosion of metal contacted by the gas when said gas also contains some waterv As hereinbefore set forth, the carboxylic acid salt of a secondary amine of the present invention possesses unique properties and serves as an effective corrosion inhibitor without the water emulsification problems encountered with salts of primary amines, for example. As hereinbefore set forth, the water tolerance property of the carboxylic acid salt ofa secondary amine permits the additive to meet military specifications especially when utilized with jet fuels.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE 1 The carboxylic acid salt of a secondary amine of this example was prepared by first dissolving 5 grams (0.01 mole) of hydrogenated N,N-ditallow amine in 7.85 grams of toluene, warming the mixture to 50 C. and then adding 2.85 grams (0.01 mole) of EMPOL 1014" acid. with intimate mixing. The N,N- ditallowamine is available commercially under the tradename Armeen ZHT and predominates in C -C alkyl groups. EMPOL 1014" is a commercially available dimeric acid and particularly dilinoleic acid. The salt was recovered as a yellow solution containing 5071 by weight of active ingredient.

EXAMPLE 11 The carboxylic acid salt of a secondary amine of this example is the hydroxystearic acid salt of hydrogenated N.Nditallowamine. The salt was prepared by first dissolving 5 grams (0.01 mole) ofArmeen 2HT in 8.11

grams of toluene with warming to about 50 C., and then intimately mixing therein 3.1 1 grams (0.01 mole) of the hydroxystearic acid. The salt was recovered as a light yellow soft solid containing 50% by weight of active ingredient.

EXAMPLE III The carboxylic acid salt of a secondary amine of this example was prepared by first dissolving 2.5 grams (0.005 mole) ofArmeen 2l-lT in 4.54 grams of tolu-' EXAMPLE IV The carboxylic acid salt of a secondary amine of this example is prepared by intimately mixing at mildly elevated temperature one acidic equivalent of palmitoleic acid and one basic equivalent of Armeen 2HT. I

EXAMPLE V The carboxylic acid salt of a secondary amine of this example is prepared by intimately mixing at mildly ele- 4 vated temperature one acidic equivalent of palmitic acid and one basic equivalent of Armeen 2HT.

EXAMPLE VI The carboxylic acid salt of a secondary amine of this example is prepared by intimately mixing at mildly elevated temperature one acidic equivalent of lignoceric acid and one basic equivalent of Armeen ZHT.

EXAMPLE VII The carboxylic acid salt of a secondary amine of this example is prepared by intimately mixing at mildly elevated temperature two basic equivalents of N,N- dicocoamine and one acidic equivalent of lactic acid in the presence of a xylene solvent.

EXAMPLE VIII The carboxylic acid salt of a secondary amine of this example is prepared by intimately mixing at mildly elevated temperature four acidic equivalents of D50 MEX acid and one basic equivalent of Armeen 2HT. As hereinbefore set forth, D50 MEX acid comprises a dimeric acid.

EXAMPLE IX As hereinbefore set forth, the carboxylic acid salt of a secondary amine of the present invention is both an effective corrosion inhibitor and passes the water tolerance specifications. The water emulsification is evaluated according to the Water Separometer Index Modified Test (WSlM). Briefly, in this test a small volume of water is added to synthetic jet fuel and the fuel is recycled. The reservoir is emptied and is passed first through a glass wool coelescer pad and then through a photocell, where the percent light transmission is measured as a determination of the turbidity of the fuel mixture. In order to pass this test, the light transmission must be at least The corrosion properties are measured according to ASTM Spindle Test D665 which also is referred to as the Steam-Turbine Oil Corrosion Test. In the modification used, hot rolled, mild-carbon steel spindles are polished and soaked in inhibited isooctane in a beaker. Synthetic sea water is added to the beaker and the system is stirred at 38 C. for hours. At the end of the test period, the spindles are rinsed and examined for rust. Less than six rust spots of less than 1 mm. diameter on a spindle is passing. Any spindle having one or more rust spots of greater than I mm. diameter also is considered as a failure.

When evaluated according to the WSIM Test described above, the carboxylic acid salt of a secondary amine prepared as described in Example I at a concentration of ppm (active ingredient) had a rating of 95. As hereinbefore set forth, this rating more than passes the 70% requirement. When evaluated according to the Corrosion Test set forth above, the salt at a concentra tion of 30 ppm will be rated as passing.

EXAMPLE X EXAMPLE XI The hydroxyphenylstearic acid salt of Armeen ZHT also was evaluated in accordance with the WSIM Test hereinbefore set forth. At a concentration of 20 ppm (active ingredient), the WSIM rating was 92. Also, when evaluated according to the Corrosion Test hereinbefore set forth, the salt at a concentration of 30 ppm will be rated as passing.

EXAMPLE XII The carboxylic acid salt of a secondary amine of this example was prepared by mixing one basic equivalent of N,N-dicyclohexylamine and one acidic equivalent of EMPOL l0l4 acid in toluene solvent in a concentration to form the salt as a 50% by weight active ingredient solution. When evaluated in the WSIM Test, the rating was at a concentration of 20 ppm (active ingredient) which, as hereinbefore set forth, will be rated as passing.

EXAMPLE XII As hereinbefore set forth, the high water tolerance of the salts used in the present invention is surprising. This is demonstrated for example in comparison with a salt of hydroxyphenylstearic acid and oleylamine. It will be noted that oleylamine is a primary amine. The oleylamine salt, when evaluated at a concentration of 20 ppm, had a WSIM rating of 31.

Another example is the hydroxystearic acid salt of oleylamine. This primary amine salt, at a concentration of 20 ppm, had a rating of 65 in the WSIM evaluation.

EXAMPLE XIV The salt prepared as described in Example V is utilized as an additive in gasoline, This serves to inhibit corrosion of metal surfaces in which the gasoline is transported and stored.

EXAMPLE XV The salt prepared in Example VI is utilized as an additive in diesel oil and serves to inhibit corrosion of metal surfaces contacted by the diesel oil.

I claim as my invention:

1. Jet fuel which is corrosive to metal on contact with water containing, as an inhibitor against corrosion, a corrosion inhibiting concentration of a secondary amine comprising a salt of hydrogenated N,N- ditallowamine and hydroxystearic acid.

2. Jet fuel which is corrosive to metal on contact with water containing, as an inhibitor against corrosion, a corrosion inhibiting concentration of a secondary amine comprising a salt of hydrogenated N,N-

ditallowamine and hydroxyphenylstearic acid. 

1. JET FUEL WHICH IS CORROSIVE TO METAL ON CONTACT WITH WATER CONTAINING, AS AN INHIBITOR AGAINST CORROSION, A CORROSION INHIBITING CONCERTRATION OF SECONDARY AMINE COMPRISING A SALT OF HYDROGENATED N,N-DITALLOWAMINE AND HYDROXYSTEARIC ACID.
 2. Jet fuel which is corrosive to metal on contact with water containing, as an inhibitor against corrosion, a corrosion inhibiting concentration of a secondary amine comprising a salt of hydrogenated N,N-ditallowamine and hydroxyphenylstearic acid. 